Density is per unit volume

length

area

space

mass

Density is mass per unit volume .

Explanation: Density is defined as the amount of mass in the space occupied (or volume)for some substance/material.

And you can calculate the density of some material by the equation:

Density = (total mass)/(total volume)

Usually density is calculated in a given amount of volume, like cm^3 and the mass used in the equation is the mass that a cm^3 of material weights

so the correct option is mass

probably not the "magnets"in the magnet, so to speak, are thought to be electrons orbiting in shells. vurrent loops two sides to the loop

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form